Several studies have examined the cognitive functions, as revealed by neuropsychological tests, of juvenile delinquents. While suggestive that delinquents may suffer from some cognitive deficits, this literature is troubled by methodological shortcomings: highly selected incarcerated or adjudicated subjects, small N's, cross-sectional design, and posthoc choice of neuropsychological tests for research. The proposed project is designed to evaluate the possibility that some patterns of neuropsychological deficit are predictive of delinquent behavior, while avoiding most of the problems characteristic of earlier research. A battery of neuropsychological tests (selected for broad coverage of a variety of cerebral functions) and the Elliott Self-Report Delinquency Interview Schedule will be administered to an unselected birth cohort of 1,000 13 year old children who are the subjects of the Dunedin Multidisciplinary Child Development Study. The Dunedin Multidisciplinary Health and Development Research Unit of the University of Otago Medical School, Dunedin, New Zealand, has studied this cohort longitudinally for 13 years, collecting and analysing data concerning the subjects' perinatal, health, psychological, educational, familial and social statuses biannually since the subjects' births. Valuable prospective data exist for the subjects, which will be used by this project to investigate possible etiological factors (e.g. birth complications or childhood head injury) for any neuropsychological deficits found to predict delinquent involvement. Existing school and family variables (e.g. learning problems, maternal attitudes toward child rearing, or social class) will be examined as possible mediating factors in any neuropsychological deficity/delinquency relationships found. The Dunedin Research Unit plans to follow up the cohort at ages 15, 17 and probably into adulthood. Neuropsychological data collected during the proposed project will then become prospective data useful for predicting a variety of deviant outcomes, including future delinquency and criminal behavior. Knowledge of delinquency-related patterns of brain dysfunction may provide information useful toward several goals: (1) Increased understanding of etiological factors in delinquency, (2) Identification of specific delinquency-related patterns of cognitive deficit which may be targeted for preventive intervention, and (3) Addition to the growing list of markers for early identification of children at risk for developing seriously delinquent lifestyles.